Whole-brain efferent projections of glutamatergic neurons in the cingulate cortex of mice

The cingulate cortex, on the medial cerebral hemisphere, is involved in cognitive processing, emotional regulation, nociception, voluntary motor control, and sleep modulation. Anatomically, the cingulate cortex is organized into three distinct subdivisions: anterior cingulate cortex (ACC, A24a/A24b), midcingulate cortex (MCC, A24a'/A24b'), and posterior cingulate cortex (PCC, A30/A29c). Although emerging evidence from rodent models has mapped cingulate cortical projections, a comprehensive characterization of whole-brain efferent pathways from glutamatergic neurons in adult mice remains incomplete. In the present investigation, we applied a homologous nomenclature system and utilized viral anterograde tracing techniques, integrating both coronal and sagittal fluorescence imaging modalities, to systematically map and reconstruct the comprehensive efferent projections of glutamatergic neurons in the ACC, MCC, and PCC of adult mice. The findings revealed that the ACC, MCC, and PCC share a conserved projection architecture with direct efferent connections to key brain regions such as the intra-cingulate cortex, cerebral cortex, subcortical telencephalon, thalamus, and brainstem. Furthermore, our analysis revealed significant heterogeneity in the spatial distribution of efferent projections among cingulate subregions. Each subregion of the cingulate cortex exhibited distinct neuroanatomical connectivity patterns, which were posited to mediate their specialized functional roles. Neuroanatomical findings provided a fundamental basis for subsequent investigations into the functional roles of glutamatergic neurons in the cingulate cortex. Moreover, these findings provided a detailed structural framework that facilitated the elucidation of neural mechanisms underlying specific physiological processes.